On the relation between orientation relationships predicted by the phenomenological theory and internal twins in plate martensite

2015 ◽  
Vol 102 ◽  
pp. 83-86 ◽  
Author(s):  
Loïc Malet ◽  
Stéphane Godet
Keyword(s):  
Phenomenological Theory ◽  
Plate Martensite ◽  
Orientation Relationships

Quantitative Analysis of Variant Selection and Orientation Relationships during the γ-to-α Phase Transformation in Hot-Rolled TRIP Steels

2010 ◽  
Vol 89-91 ◽  
pp. 359-364 ◽  
Author(s):  
Loïc Malet ◽  
Pascal J. Jacques ◽  
Stéphane Godet
Keyword(s):  
Phase Transformation ◽  
Orientation Relationship ◽  
Hot Deformation ◽  
High Performance ◽  
Statistical Treatment ◽  
Phenomenological Theory ◽  
Variant Selection ◽  
Orientation Relationships ◽  
Α Phase ◽  
Hot Rolled

The orientation relationships that apply to the fcc (γ) – bcc (α) phase transformation in high-performance hot-rolled TRIP-aided steels were characterised by EBSD techniques. A statistical treatment of the experimental data allows the mean orientation relationship to be determined. This mean orientation relationship was compared to the models commonly proposed in the literature and confronted qualitatively to the predictions of the phenomenological theory of martensite crystallography (PTMC). The variant selection phenomenon was also characterized quantitatively at the level of individual austenite grains. The reconstruction of the EBSD maps evidences that bainite grows by packets in which the bainite laths share a common {111}γ plane in the austenite. This growth mechanism is not influenced by the prior hot deformation of the austenite. The hot deformation has a critical influence on the number of packets that forms. The analysis of the crystallographic features of the bainite packets reveals that all possible variants are formed in a packet, though in different proportions.

Phase Transformation Crystallography of Lath Martensite

2006 ◽  
Vol 979 ◽  
Author(s):  
Xiao Ma ◽  
R.C. Pond
Keyword(s):  
Phase Transformation ◽  
Habit Plane ◽  
Lath Martensite ◽  
Martensitic Transformations ◽  
Phenomenological Theory ◽  
Orientation Relationships ◽  
Transformation Mechanism ◽  
Ferrous Alloys ◽  
Model Phase ◽  
Good Agreement

AbstractOur current understanding of martensitic transformations has been based on the Phenomenological Theory of Martensite Crystallography developed in the 1950s. Recently, a Topological Model of martensitic transformations has been presented wherein the habit plane is a semi-coherent structure, and the transformation mechanism is shown explicitly to be diffusionless. This approach is used here to model phase transformation crystallography of lath martensite in ferrous alloys. A range of network geometries is predicted corresponding to orientation relationships varying from Nishiyama-Wasserman to Kurdjumov-Sachs. Experimental observations from the literature of the dislocation and disconnection arrays, habit plane and orientation relationship are in good agreement with the model.

Use of 2½ D imaging in analysis of NiTi martensite

1978 ◽  
Vol 36 (1) ◽  
pp. 610-611
Author(s):  
G. M. Michal
Keyword(s):  
Memory Effect ◽  
Monoclinic Phase ◽  
Reaction Path ◽  
Structural Characteristics ◽  
Salient Feature ◽  
Martensite Phase ◽  
Orientation Relationships ◽  
Low Symmetry ◽  
Hydride Phases ◽  
Unusual Shape

Several TEM investigations have attempted to correlate the structural characteristics to the unusual shape memory effect in NiTi, the consensus being the essence of the memory effect is ostensible manifest in the structure of NiTi transforming martensitic- ally from a B2 ordered lattice to a low temperature monoclinic phase. Commensurate with the low symmetry of the martensite phase, many variants may form from the B2 lattice explaining the very complex transformed microstructure. The microstructure may also be complicated by the enhanced formation of oxide or hydride phases and precipitation of intermetallic compounds by electron beam exposure. Variants are typically found in selfaccommodation groups with members of a group internally twinned and the twins themselves are often observed to be internally twinned. Often the most salient feature of a group of variants is their close clustering around a given orientation. Analysis of such orientation relationships may be a key to determining the nature of the reaction path that gives the transformation its apparently perfect reversibility.

Moire Fringes on Precipitates in Quenched and Aged Beryllium

1968 ◽  
Vol 26 ◽  
pp. 426-427
Author(s):  
F. J. Fraikor ◽  
A. W. Brewer
Keyword(s):  
Ternary Phase ◽  
Volume Fraction ◽  
Age Hardening ◽  
Orientation Relationships ◽  
Solute Content ◽  
Moiré Fringes ◽  
Moire Patterns ◽  
Total Volume Fraction ◽  
Diffraction Patterns ◽  
Moiré Patterns

A number of investigators have examined moire patterns on precipitate particles in various age-hardening alloys. For example, Phillips has analyzed moire fringes at cobalt precipitates in copper and Von Heimendahl has reported on moire fringes in the system Al-Au. Recently, we have observed moire patterns on impurity precipitates in beryllium quenched in brine from 1000°C and aged at various temperatures in the range of 500-800°C. This heat treatment of beryllium rolled from vacuum cast ingots produces the precipitation of both an fee ternary phase, AlFeBe4, and an hcp binary phase, FeBe11. However, unlike a typical age-hardening alloy, the solute content of this material is low (less than 1000 ppm of Fe and 600 ppm of Al) and hence the total volume fraction of precipitates is small. Therefore there is some difficulty in distinguishing the precipitates and their orientation relationships with the beryllium matrix since the weak precipitate spots generally do not appear on the diffraction patterns.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

Direct imaging of order-disorder and antiphase domain structures in Ti3Al intermetallic compound

1990 ◽  
Vol 48 (4) ◽  
pp. 480-481
Author(s):  
H. Q. Ye ◽  
T.S. Xie ◽  
D. Li
Keyword(s):  
Intermetallic Compound ◽  
Volume Fraction ◽  
Fundamental Problem ◽  
Antiphase Domain ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Domain Structures ◽  
Α Phase ◽  
Diffraction Patterns ◽  
Two Phases

The Ti3Al intermetallic compound has long been recognized as potentially useful structural materials. It offers attractive strength to weight and elastic modulus to weight ratios. Recent work has established that the addition of Nb to Ti3Al ductilized this compound. In this work the fundamental problem of this alloy, i.e. order-disorder and antiphase domain structures was investigated at the atomic scale.The Ti3Al+10at%Nb alloys used in this study were treated at 1060°C and then aged at 700°C for 2 hours. The specimens suitable for TEM were prepared by standard jet electrolytic-polishing technique. A JEM-200CX electron microscope with an interpretable resolution of about 0.25 nm was used for HREM.The [100] and [001] projections of the α2 phase were shown in Fig.l.The alloy obtained consist of at least two phases-α2(Ti3Al) and β0 structures. Moreover, a disorder α phase with small volume fraction was also observed. Fig.2 gives [100] and [001] diffraction patterns of the α2 phase. Since lattice parameters of the ordered α2 (a=0.579, c=0.466 nm) and disorder α phase (a0=0.294≈a/2, c0=0.468 nm) are almost the same, their diffraction patterns are difficult to be distinguished when they are overlapped with epitaxial orientation relationships.

Optical Properties and Phenomenological Theory of Ferri-Ferri Phase Transitions in Antiferroelectric Liquid Crystals

1997 ◽  
Vol 7 (12) ◽  
pp. 1817-1828 ◽  
Author(s):  
P. Gisse ◽  
M. Sidir ◽  
V. L. Lorman ◽  
R. Farhi ◽  
J. Pavel ◽  
...  
Keyword(s):  
Optical Properties ◽  
Phase Transitions ◽  
Liquid Crystals ◽  
Phenomenological Theory ◽  
Antiferroelectric Liquid Crystals

The Thanatosis of Enlightenment

2019 ◽  
Vol 29 (4) ◽  
pp. 83-106
Keyword(s):  
Scientific Reasoning ◽  
Phenomenological Theory ◽  
Human Mind ◽  
Unsuccessful Attempt ◽  
Trace Back ◽  
Methodological Errors ◽  
Psychological Models ◽  
History Of ◽  
Living Nature ◽  
Dialectic Of Enlightenment

The article analyzes methodological errors Theodore Adorno and Max Horkheimer’s Dialectic of Enlightenment, particularly their incorrect use of the concepts of mimicry and mimesis. The author of the article maintains that the leaders of the Frankfurt School made a mistake that threatens to undermine their argument when they juxtaposed mimesis and the attraction to death, which has led philosophers to trace back to mimesis the desire for destruction that is found in a civilization constructed by instrumental reasoning. The author reviews the arguments of the Dialectic of Enlightenment and emphasizes the unsuccessful attempt to fuse Freudian and Hegelian methods, which exposes the instability of opposing scientific reasoning to “living” nature. Some amusing quotations from Roger Caillois, who refused to think of mimesis as something entirely rational, are also brought to bear. As Brassier gradually unfolds Adorno and Horkheimer’s thesis, he indicates the consequences of their mistake, which confined thinkers to the bucolic dungeon of “remembering” the authentic nature that they cannot abandon because they have denied themselves access to both reductionist psychological models and to phenomenological theory as such. Brassier delineates the boundaries of this trap and notes the excessive attachment of the Dialectic of Enlightenment to the human. Brassier goes on to describe the prospects for a civilization of enlightenment: a mimesis of death in both senses (death imitates and is imitated) finds its highest expression in the technological automation of the intellect, which for Adorno and Horkheimer means the final implementation of the self-destructive mind. However, for Brassier it means the rewriting of the history of reason in space. This topological rewriting of history, carried out through an enlightenment, reestablishes the dynamics of horror more than mythical temporality: it will become clear that the human mind appears as the dream of a mimetic insect.

scholarly journals Superconducting Order Parameter Nucleation and Critical Currents in the Presence of Weak Stray Fields in Superconductor/Insulator/Ferromagnet Hybrids

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 507
Author(s):  
Vasiliy N. Kushnir ◽  
Serghej L. Prischepa ◽  
Michela Trezza ◽  
Carla Cirillo ◽  
Carmine Attanasio
Keyword(s):  
Phenomenological Theory ◽  
Critical Currents ◽  
Superconducting Phase ◽  
Stray Field ◽  
Superconducting Properties ◽  
Ginzburg Landau ◽  
Ferromagnetic Layers ◽  
Linearized System ◽  
Critical Current Density Jc ◽  
Usadel Equations

The stray fields produced by ferromagnetic layers in Superconductor/Insulator/Ferromagnet (S/I/F) heterostructures may strongly influence their superconducting properties. Suitable magnetic configurations can be exploited to manipulate the main parameters of the hybrids. Here, the nucleation of the superconducting phase in an external magnetic field that periodically oscillates along the film width is studied on the base of the numerical solution of the linearized system of Usadel equations. In addition, the effect of the magnetic configuration of the F-layer on the temperature dependence of the critical current density, Jc(T), is investigated in the framework of the Ginzburg–Landau phenomenological theory on the base of the oscillating model of a stray field. By following this approach, the Jc(T) dependence of a Nb/SiO2/PdNi trilayer is reproduced for different magnetic configurations of the PdNi layer.

Sign in / Sign up

Export Citation Format

Share Document